This is a NIH-funded multi-center study of the relationship between sleep-disordered breathing and cardiovascular disease. It is being performed in subjects who are already being evaluated for cardiovascular disease either as patients or as volunteers in an existing study. Progress report and summary of findings: The first year and a half was spent forming a common protocol, which involves collecting some additional clinical data (in this case items such as the ankle arm index and spirometry) and performing homo polysomnography, using a new battery- operated ambulatory recording system developed by compumedics, an Australian company. It was decided to compress the enrollment of subjects into two years, from December of 1995 to January of 1998, and to shift most of the 5 year budget into this period. Enrollment has just been completed, and the investigators have completed 760 successful studies altogether. The ethnic breakdown of the cohort is 70% White, 20% Black, 5% Asian and 5% Hispanic. Approximately equal numbers of Black subjects have been recruited from Cornell and Harlem. The investigators are about to begin the one year follow-up visits, which will consists of a brief clinic visit and questionnaire. The Sleep Heart Health Study terminates in September of 1999, by which time there will clearly not be enough new morbid events to enable the major hypothesis to be tested, and this issue will be addressed in a continuation proposal.